I've leveled two characters to 100 now (believe me, not because I wanted to, first one was because my server had 10 hour queues for days) and i've learned a great deal of things that might come in handy, thought i'd share.

First of all, if you want garrison resources long-term, you're gonna want to say fuck the lumber mill and go for a trading post instead. Trading posts produce 50% more resources in the same amount of time, but consume random trade goods instead of "timber". But you'll get lots of fur just from leveling, TONS of ore because of the mine, lots of various types of herbs from the herb garden, etc. Work orders are all 4 hours each and it changes daily for the trading post, so even if its something you don't really wanna give up, you wouldn't have to give up a whole lot of it to make it through the day, and when it turns to something you have tons of and don't care much for like blackrock ore, you can fill that bitch to the limit.

Next, as soon as is possible you're gonna want to bulldoze that barracks and replace it with a War Mill or Dwarven Bunker. Having double the rate for quest items being upgraded is HUGE. Now for most of the leveling process this doesn't matter at all because your SOO gear will practically last to 100 if its mythic and has gems. But the real advantage of this is if you have your mill/bunker up and running when you hit 98, immediately stop doing whatever zone you're doing and goto nagrand to finish the grind to 100. The quest rewards are much higher item level and when they proc epic, its better than dungeon gear. You can be over 610 ilevel by the time you hit level 100 allowing you to bypass normal dungeons entirely and go straight into heroics. Long-term, you'll probably want one of these buildings anyway cause of the free seal of fate each week. Buying all 3 every week will put a serious strain on your resources. Buying two each week is bad enough.

Now maybe the trading outpost isn't for you, maybe you already bought a lumber mill, maybe you don't want to spend valuable trade goods on garrison resources. Lumber mill is still 2nd best building for generating resources. Just keep in mind upgrading it to level 2 does NOT increase the yield on resources. Literally the only effects it has is allowing you to harvest medium trees (which yield ~10 timber as opposed to smalls yielding ~5) and increasing the number of workorders. Number of work orders is rather pointless because as long as you log in at least once per day you'll keep that full, and small timber is plenty to keep your mill churning out the goods non-stop, the medium and large trees simply aren't needed. You basically have to cut down 2 small trees for every 4 hours you want your mill to run, at level 2, you'd have to cut down 1 medium for every 4 hours. So you really aren't that much better off there. SO save your shit, don't spend it on level 2 unless you plan on (and have the means to) goto level 3 immediately from level 1. Level 3 unlocks (in a roundabout way) a new follower you can assign to the mill that increases resource production by 50% making it equal to trading outpost. This is the only way you can actually get more resources from upgrading your thing. If you do decide to go level 2 lumber mill, theres an item you can get that will let you drop combat whenever you want in outdoor draenor zones on a 5 min CD, it also only costs 200 resources instead of 300 to upgrade it, because you get 100 back as kind of a rebate for a quest you get after going level2.

Now as far as little buildings go, don't do work orders unless you have a profession equal to that building's profession. There is NO point. Workorders produce the same crap people with the profession make with their daily cooldown, but it's all BOP. So you can't sell it on the AH, you can't trade it to your alts, if you have no means of using that resource, it is pointless. ALchemy lab is a good example of this because it makes catalysts which is great if you're an alchemist, but literally can't do anything if you aren't. It just consumes your frostweed for no reason. There are a few exceptions to this though, like if you're a platewearer, even if you dont have blacksmithing you could use a forge and it's work orders to eventually make enough truesteel to craft you an epic item or two. Keep in mind though, the amount you need to craft this crap coupled with the rate workorders produce truesteel, you're looking at over 2 weeks of non-stop workorder time per item crafted. Same is true for clothies and the tailoring shack, etc.

Speaking of frostweed, when you upgrade your herb garden to level 2 and assign a herbalist follower to it, you can choose what you want to grow there, so every single herb node will be a single type of chosen herb. You just talk to the chick that sells the overpriced gardening equipment.

If you REALLY want to pump out the garrison resources at any cost, you can use the stables as one of your large buildings. I don't think it is ever mentioned anywhere, but those quests and dailies for dealing with all that mount taming mess gives you resources for each mission. I think in total you get something like 1600 resources for doing all related quests, plus you get 6 mounts so theres that too. Even when you consider the money wasted by replacing this building later, it's very worth it. This might also be a good choice for people looking to maximize their garrisons quickly who already leveled without making a war mill yet. The level 3 war mill blueprints (which has the bonus nearly everyone wants) isn't gonna be available to you for a long ass time. It's gonna take significant time and garrison resource investment to level 20 followers to 100.

Speaking of followers, don't try to carry them. Make them sum bitches carry their own weight on missions. You aren't going to be able to make some badass carry team to level some level 90 piece of shit and power level it like you would do with battle pets. It dont work that way. Even if they are ONE LEVEL lower than the mission level, they only get half XP. When 3 or more levels lower, they only get 10%. So forget that noise. Make them do their own missions. They also gain full XP for the mission even if they fail it, so if you want to power level them fast, just send them on juicy XP missions of the same level. Sending a level 90 solo on a level 100 mission will still apply the whole "only 10% xp gained" crap though so yeah. You won't get the bonus xp for completing, but you always get the base XP which is pretty significant.

Missions that grant garrison resources also never cost garrison resources to send people on i've found, so even if you're whoring up your resources and dont want to spend on sending people on missions, you can keep an eye out for those missions to send people on because it doesn't cost anything.

Now i've been awake far too long and in this state too often too many times lately so i'm going to sleep. Maybe this stuff will help someone.